Single-Tray VLM vs Dual-Tray VLM: Quantitative Throughput Comparison

Abstract

In this paper quantitative comparison of resulting throughputs for single-tray and dual-tray VLM devices is presented. Comparison is based on mathematical models for throughput approximating dual command times of VLM’s crane, for selected parameters of VLM device (height and crane’s velocity) and selected picking times per delivered tray. Analysis showed that throughput increase achieved by using dual-tray VLM’s depends mostly on the average picking time relative to the expected dual command time of the VLM’s crane. Highest improvements are possible for picking time equal to expected dual command time and amounts over 80%, however for extremely low or high picking times improvements are significantly reduced.

Keywords

• dual-tray VLM
• order-picking
• single-tray VLM
• throughput model
• vertical lift module systems